Electric furnace.



J. L. mxow. ELECTRIC FURNACE.

APPLICATION FIL ED AFR-10. 1916.

Patented Sept. 19,1916.

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To all whom it may concern;

Be it known that l, Josnrni L. BIXUN? a subject of the King of GreatBritain, residing in the city of Detroit and State of Michigan, haveinvented certain new and useful Improvements in Electric liurnaces anddo hereby declare the following to be of electric smelting furnaceswherein the current may be made to pass either from one electrode toanother over the bath or from one or more of these either wholly or inpart through the bath and furnace lining.

The object of my invention is to supply an improved construction forelectric smelt ing furnaces of this kind whereby threephase currents fedfrom specially arranged transformers are made controllable to theirphase relations by suitable-switches, so as to cause differentproportions of the total current to flow through the bath and lining Itis a further object of the, invention to so accomplish this that amaximum of flexibility in such current changes may be attained, and to 0this without unbalancing the load on the feeding mains.

A preferred embodiment of the invention is illustrated diagrammaticallyin the ac-' companying drawings wherein- Figure 1 shows a furnace havingtwo groups of three upper electrodes supplied with three-phasealternating current and Figs. 2 and 3 are vector diagrams illustratingdifferent phase conditions produced by certain changes in the electricconnections shown in Fig.

In Fig. 1, the usual'hearth, crucible or container is shown at 10, themolten bath within it is shown at 11 while the six upper electrodes 12,13.14, 15, lfiand ll project downward toward the bath through the insulating cover 18. The current which passes downward through the bath,when so desired returns through the lower electrode 19. The workingcurrent is derived from the threephase alternating current mains, 20, 21and 22 through two groups of three transformers shown respectively at23; 2 1 and 25 and at 26, 27 and 28. The three primaries of thetransformers 23, 24- and25 are connect 1. Elle. 55,1 32. iserial 83,652,

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kairidec'l and this application filed [April 10,

gular connection with the leads or mains 39,391 and 22; while theremaining three transformers 26, 27 and 28 are coniected in starfashion. A common. conducor leads "to the lower electrode 19, and tothis one is connected one terminal of each of the secondaries of all thetransformers. The remaining secondary terminal of each transformerconnected to its appropriate upper terminal, as shown.

While I have shown one three-transformer group fed by triangularlyconnected conductors and one such group combined therewith as describedand fed by star-connected conductors, it is to be understood that myinvention is notlimited to the use of a single group of each kind butcovers combinations of triple groupsof these two kinds whether one ormore of each of such 1 groups is used.

system; and other modes of changing con nections may be used foraltering the phase relations without departing from my invention.

.When the switches 31 are closed and switches 30 are open the phaserelations shown in Fig. 3 are obtained. in this case, assuming thecurrents to be equal in all of the upper electrodes, the value of vthecurrent through the bath will be zero. When, on the other hand, switch31 is open and switch 30 is closed, the phase relations will be asindicated in 3. In this case, assuming currents of equal unit magnitudesin the upper electrodes, the value of the current through the bath willbe 1.0%. Uther possible arrangements willvbe obvioils, and by increasingthe number of shade aveilanla lay choice at it as:

which various proportions of current fiow may be made to reach the lowerelectrode through the bath,

By using two groups of transformers, one connected to the supply mainsin triangular and the other in star fashion the proportion of currentwhich may be caused to flow through the bath to the electrode can .bemuch more extensively varied than would be possible if the electrodeswere fed from groups of transformers delivering threephasestar-connected currents in the ordinary manner. In such ordinary cases,the only changes available are those brought about by the reversal ofone phase, which,

in the case of a furnace with six upper electrodes causes the current inthe lower electrode to be four times as great as that in each of theupper electrodes.

This application is a division of my earlier application for improvementin electric furnaces, filed February 23, 1915, Serial No. 9782.

-What I claim is:

1. An electric furnace having a lower electrode and two or more groupsof three upper electrodes, main leads for supplying threephasealternating current, transformers in groups of three corresponding innumber with said upper electrodes, and having their secondary coilssuitably connected with said upper and lower electrodes, conductors con-Gopies of this patent may be obtained for five cents each, by addressingthe Commissioner of Patents,

ductors connecting the primaries of one or more of saidthree-transforiner groups to triangular fashion, one or more similar.

groups connected with said main leads in star-fashion, and suitableswitches arranged to reverse the terminal connections of one primary ineach triangularly connected group with relation to two of said mainleads.

4. In a heating equipment for electric'furnaces, main leads forsupplying three-phase alternating current, one or more. groups of threetransformers having their priniary coils connected to said leads intriangular fashion, one or more similar groups connected with said mainleads in star fashion, and suitable switches arranged to reverse theterminal connections of one primary in each star connected group withrespect to the interior or common connection of the star.

4. In a heating equipment for electric furnaces, main leads forsupplying three-phase alternating current, one or more groups of threetransformers having their primary coils connected to said leads intriangular fashion, one or more similar groups connected with said mainleads in star fashion, and two 0 more sets of multiple switches arrangedto reverse the terminal connections of one primary in each triangularlyconnected group with relation to two of said main leads, while alsoreversing the terminal connections of one primary in each star connectedgroup with respect to the interior or common connection of the star.

In testimony whereof, I have affixed my signature.

JOSEPH LAWTON DIXON.

Washington, D. G.

